package demo1;

import java.util.Arrays;

public class TestHeap {
    public int[] elem;
    public int usedSize;

    public TestHeap() {
        this.elem = new int[10];
    }

    public void initElem(int[] array) {
        for (int i = 0; i < array.length; i++) {
            this.elem[i] = array[i];
            this.usedSize++;
        }
    }

    public void createHeap() {
        for (int parent = (this.usedSize-1-1)/2; parent >= 0 ; parent--) {
            siftDown(parent,this.usedSize);
        }
    }
    /**
     * @param parent 每棵子树调整的时候 的 起始位置
     * @param usedSize 判断 每棵子树什么时候 调整 结束
     */
    private void siftDown(int parent, int usedSize) {
        int child = 2*parent+1;
        while (child < usedSize) {
            //找到左右孩子的最大值
            if(child+1 < usedSize && elem[child] < elem[child+1]) {
                child++;
            }
            if(elem[child] > elem[parent]) {
                swap(elem,child,parent);
                parent = child;
                child = 2 * parent + 1;
            }else {
                break;
            }
        }
    }

    private void swap(int[] elem,int i,int j) {
        int tmp = elem[i];
        elem[i] = elem[j];
        elem[j] = tmp;
    }


    public void offer(int val) {
        if(isFull()) {
            elem = Arrays.copyOf(elem,2*elem.length);
        }
        elem[usedSize] = val;
        siftUp(usedSize);
        usedSize++;
    }

    private void siftUp(int child) {
        int parent = (child-1)/2;
        while (parent >= 0) {
            if(elem[child] > elem[parent]) {
                swap(elem,child,parent);
                child = parent;
                parent = (child-1)/2;
            }else {
                break;
            }
        }
    }

    public boolean isFull() {
        return usedSize == elem.length;
    }

    public int poll() {
        if(isEmpty()) {
            return -1;
        }
        int val = elem[0];
        swap(elem,0,usedSize-1);
        siftDown(0,usedSize-1);
        usedSize--;
        return val;
    }
    public boolean isEmpty() {
        return usedSize == 0;
    }

    public int peek() {
        if(isEmpty()) {
            return -1;
        }
        return elem[0];
    }

    //O(N) + o(n*logN) ->  o(n*logN)
    public void heapSort() {
        int end = usedSize-1;
        while (end > 0) {
            swap(elem,0,end);
            //本来堆已经就是最大堆，此时相当于最后一个值一定是最大值，故检查是否排完毕时，最后一个就不用管
            //相当于，usedsize就变为了usedSize-1,即end
            //这里重新进行堆排序
            siftDown(0,end);
            end--;
        }
    }
}
